The present invention relates to a device for measuring at least one physical parameter relating to a game ball propelled by means of a striking element, in particular a tennis racket, as well as a tennis racket fitted with such a measuring device, this device comprising at least one measuring sensor mounted on the said striking element and designed to send signals corresponding to said physical parameter to be measured, means of processing these signals designed to analyse the signals sent by the measuring sensor and to work out a measured value of said physical parameter and display means for displaying this value, the measuring sensor being designed to detect the vibrations caused by the ball propelled by the striking element and comprising a piezoelectric element designed to send sinusoidal electric signals in proportion to the severity of the vibrations detected.
"Physical parameter" means in particular the speed of an appropriate ball propelled by a corresponding striking element, or any other variable such as the force with which the ball is struck or similar. The invention can therefore apply to all games or sports involving a ball and a striking element, such as tennis, golf, baseball, ice hockey, and table tennis along with others, with no limitation. Tennis has been chosen as an example of an application in the present invention.
It is well known in the sporting world that players are continually striving to improve their performances. This is why we seek to develop means of measuring, calculating and comparing these performances. Nevertheless, at the present time, there are no means available making it possible to sufficiently accurately and reliably measure the speed of a ball in real time during a game. In high-level sporting events, it is common to use radars placed at the edge of the playing area. The latter require considerable investment and provide results whose error margin of approximately 20% makes them unusable. Stopwatches are also used, which make it possible to work out the speed of the ball by integrating the distance and the time. However, this system is too complicated to manage.
There are nevertheless some measuring devices provided in a striking element such as a racket or a golf club which are designed to measure the force with which a ball is struck or the ball's point of impact on the striking element. These devices are described in particular in the following publications DE-A-34 36 218, U.S. Pat. No. 4,991,850, U.S. Pat. No. 4,870,868 and U.S. Pat. No. 4,008,324. However, none of them is designed to instantaneously provide a measured value corresponding to the speed with which a ball is struck.
The aim of the present invention is to overcome the above-mentioned drawbacks by proposing a very inexpensive measuring device, which is extremely compact and can be fully fitted onto the striking element, capable of instantaneously providing a value for said physical parameter by way of a real-time measurement, ensuring accuracy to within about 5%, and able to be calibrated quickly according to the type of striking element and the type of game ball without the need for additional, sophisticated calibrating equipment.
The aim is achieved by a measuring device as described in the preamble and characterised in that the physical parameter corresponds to the speed at which the game ball is struck.